Conventionally, a semiconductor device manufacturing process is performed in a clean room with high cleanliness. However, along with the scaling up of a semiconductor wafer (hereinafter, referred to as “wafer”) and various processing apparatuses for processing a wafer, a running cost for the clean room is increased. For this reason, there is recently employed a method for maintaining, at high, only cleanliness in processing apparatuses and in a substrate container, referred to as a FOUP (front opening unified pod) which is used for exchanging wafers between processing apparatuses.
The above-described substrate container is configured to be able to accommodate a plurality of wafers in multiple stages in parallel to each other and configured to load/unload wafers through an opening formed at one side of the substrate container. The substrate container is filled with nitrogen gas of high cleanliness to prevent contaminants such as particles or the like entering the substrate container.
However, the substrate container accommodates a wafer processed by the processing apparatus as well as an unprocessed wafer. Therefore, particles adhered to a wafer in the processing apparatus may be brought into the substrate container. In that case, other wafers are contaminated by the particles, which may lead to deterioration of a product yield.
As for a method for removing particles adhered to a wafer, there is disclosed in, e.g., Patent Document 1 a method for purging the interior of a substrate container by introducing a purge gas of high cleanliness from a lower portion of the substrate container.